1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a method of manufacturing a color filter substrate of an LCD device.
2. Discussion of the Related Art
Currently, various display devices are in high demand. Accordingly, many efforts have been made to research and develop various flat display devices such as liquid crystal display (LCD), plasma display panel (PDP), electroluminescent display (ELD), and vacuum fluorescent display (VFD). Some of the types of flat display devices have already been included in displays for various types of equipment.
Among the various flat display devices, liquid crystal display (LCD) devices have been most widely used due to their advantageous characteristics. For example, LCD devices have a thin profile, are lightweight, and consume a low amount of power. Accordingly, an LCD device is a substitute for a Cathode Ray Tube (CRT). In addition to LCD devices used in mobile equipment, such as displays for notebook computers, LCD devices have been developed for computer monitors and televisions to receive and display broadcasting signals.
An LCD device typically includes an LCD panel that displays images and a driver that applies a driving signal to the LCD panel. The LCD panel may include first and second glass substrates bonded together at a predetermined interval and a liquid crystal layer formed between the first and second substrates.
The first glass substrate, for example a TFT array substrate, may include a plurality of gate lines, a plurality of data lines, a plurality of pixel electrodes, and a plurality of thin film transistors. The plurality of gate lines are formed at fixed intervals in a first direction, and the plurality of data lines are formed at fixed intervals in a second direction substantially perpendicular to the first direction, to thereby define a plurality of pixel regions. Then, the plurality of pixel electrodes, which are arranged in a matrix, are respectively formed in the pixel regions. The plurality of thin film transistors are switched according to signals on the gate lines so as to transmit signals on the data lines to the respective pixel electrodes.
The second glass substrate, for example, a color filter substrate, may include a black matrix layer that excludes light from regions except the pixel regions of the first glass substrate, R(red)/G(green)/B(blue) color filter layers displaying various colors, and a common electrode to represent the picture image.
Also, spacers may be provided between the first and second glass substrates. Then, the two glass substrates may be bonded to each other by a sealant. Subsequently, liquid crystal may be injected into a space between the first and second glass substrates, to thereby form the liquid crystal layer.
The color filter layer produces various colors in the image. The color filter layer includes three-color filters that transmit predetermined wavelengths of light.
Each pixel region corresponds to a first dot that displays color and is divided into three sub pixels. In this state, red (R), green (G), and blue (B) color filters are arranged in the respective sub pixels, to thereby realize full-color images.
The color filter layer may be manufactured by various methods. The methods include, for example, a pigment-spraying method, a printing method, an electro-deposition method, and a thermal-printing method. The pigment-spraying method has an excellent color realization ratio, but requires long and complicated processing. The printing method requires a simpler process, but cannot be applied to a large-sized display device because the printing method is not very elaborate. The electro-deposition method may produce flat color filter layers having color filters that do not vary in thickness. However, the electro-deposition method may produce poor picture quality.
The thermal-printing method may be a dry-etching process. In the thermal-printing method, a printing film including a color material is formed on a substrate, and then a light source, such as laser beam, is applied to the substrate, whereby the color material of the printing film is transcribed to the substrate. The printing film may be a red (R), green (G), or blue (B) printing film.
A related art thermal-printing method for manufacturing a color filter substrate of an LCD device is explained as follows.
As shown in FIG. 1A, black matrix patterns 12 are formed on predetermined portions of a substrate 10. Then, a printing film 14, which is used to form a first color filter layer, is positioned at a predetermined interval from the substrate 10 including the black matrix patterns 12. The printing film 14 may include a supporting layer 14a, a transforming layer 14b that transforms light energy into heat energy, and a first color printing layer 14c. The printing film 14 may be tightly adhered to the substrate 10 by vacuum.
As light is applied by a light source to the supporting layer 14a of the printing film 14, the transforming layer 14b absorbs the light and emits heat. The first color printing layer 14c is thereby transcribed to the substrate 10 due to the emitted heat. A first color filter layer 16a is thus formed on the substrate 10.
The light source may include a laser head, wherein a laser beam is emitted from the laser head.
As shown in FIG. 1B, the above process is repetitively performed using second and third color printing layers (not shown), to thereby form second and third color filter layers 16b and 16c. Then, the color filter layers 16a, 16b and 16c may be cured at a temperature between 200° C. and 300° C.
As shown in FIG. 1C, after completing the curing process, an overcoat layer 18 may be formed on the substrate 10. Then, a common electrode layer 20 may be formed on the overcoat layer 18 by sputtering or E-beam.
The overcoat layer 18 is formed on a display area inside a sealant on the substrate. The overcoat layer 18 is not formed in a non-display area. The overcoat layer 18 is formed by coating an organic insulating material on an entire surface of the substrate 10 and patterning the coated organic insulating material by photolithography. The photolithography required for forming the overcoat layer 18 is necessarily complicated. Thus, manufacturing costs are increased.